While en route, the pilot radioed that they had encountered rough weather and were turning back. The hospital lost contact with the helicopter a short time later, Maher said.

Eric Weiss, spokesman for the National Transportation Safety Board, which is leading the investigation, says initial reports show the helicopter left Rockford in freezing rain that "impacted the terrain southwest of Rochelle."

A preliminary report on the crash will be available within 10 days and the full report will be completed in the next 12 to 18 months, Weiss said. The Federal Aviation Administration is assisting.

Lee County Sheriff's deputies were called about 8:30 p.m. after a farmer reported that the helicopter crashed in a cornfield near U.S. Route 30 and state Route 251, near Melugins Grove Road south of Rochelle.

Deputies received a call 15 minutes earlier from Rockford after the hospital lost radio contact with the crew somewhere over the southeast part of the county, Varga said.

Deputies and state police, and Compton and Paw Paw fire responded to the scene. An investigator from the NTSB was en route, Varga said.

The wreckage covered an area about the size of one and a half football fields, Varga said.

Rockford Health Systems started its REACT program in 1987 and bought its MBBK 117 helicopter in 1991. This is the program's first crash in more than 10,000 transports, Maher said.

Dillow started at Rockford Memorial Hospital in 1996 and was an experienced critical care nurse and emergency room nurse. He had more than 10 years experience as a flight nurse.

Hollis has been with the hospital since 1986 as a critical care nurse. She was a clinical resource coordinator and trauma nurse coordinator and also had more than 10 years experience as a flight nurse.

Olesen was employed by Air Methods, the hospital's contracted provider of aircraft services, since 1994 and had been a pilot for REACT for about 5 years.

He was planning to retire next week, his pastor, the Rev. Ralph Kuespert of Bethlehem Lutheran Church in Rockford, told the Journal-Standard in Freeport.